Improve members email listing

Add new options to list only subscribers and subscribers to a given offer.

--subscribers lists email addresses of subscribers to any offers.
--offer OFFER-ID or OFFER-REF lists email addresses of subscribers to the specified offer.

Was related to #86

coin/members/management/commands/members_email.py

@@ -1,15 +1,58 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 
+import datetime
+
 from django.core.management.base import BaseCommand, CommandError
+from django.db.models import Q
 
 from coin.members.models import Member
-
+from coin.offers.models import Offer
+from coin.offers.models import OfferSubscription
 
 class Command(BaseCommand):
-    help = 'Returns the email addresses of all members, in a format suitable for bulk importing in Sympa'
+    help = """Returns email addresses of members in a format suitable for bulk importing in Sympa."""
+
+    def add_arguments(self, parser):
+        parser.add_argument('--subscribers', action='store_true',
+                            help='Return only the email addresses of subscribers to any offers.')
+        parser.add_argument('--offer', metavar='OFFER-ID or OFFER-REF',
+                            help='Return only the email addresses of subscribers to the specified offer')
 
     def handle(self, *args, **options):
-        emails = [m.email for m in Member.objects.filter(status='member')]
+        if options['subscribers']:
+            today = datetime.date.today()
+                        
+            offer_subscriptions = OfferSubscription.objects.filter(
+                Q(resign_date__gt=today)
+                | Q(resign_date__isnull=True)
+            )
+            members = [s.member for s in offer_subscriptions]
+        elif options['offer']:
+            try:
+                # Try to find the offer by its reference
+                offer = Offer.objects.get(reference=options['offer'])
+            except Offer.DoesNotExist:
+                try:
+                    # No reference found, maybe it's an offer_id
+                    offer_id = int(options['offer'])
+                    offer = Offer.objects.get(pk=offer_id)
+                except Offer.DoesNotExist:
+                    raise CommandError('Offer "%s" does not exist' % options['offer'])
+                except (IndexError, ValueError):
+                    raise CommandError('Please enter a valid offer reference or id')
+            today = datetime.date.today()
+
+            offer_subscriptions = OfferSubscription.objects.filter(
+                 # Fetch all OfferSubscription to the given Offer
+                Q(offer=offer)
+                # Check if OfferSubscription isn't resigned
+                & (Q(resign_date__isnull=True) | Q(resign_date__gt=today))
+            ).selec_related('member')
+            members = [s.member for s in offer_subscriptions]
+        else:
+            members = Member.objects.filter(status='member')
+
+        emails = list(set([m.email for m in members if m.status == 'member']))
         for email in emails:
             self.stdout.write(email)